The present invention relates to copolymer solutions based on addition products of .alpha., .beta.-unsaturated carboxylic acid with glycidyl esters and copolymerisable .alpha., .beta.-unsaturated monomers with and without hydroxyl groups. The present invention also relates to the preparation of such hydroxyl-containing copolymers and to the use thereof in clear or pigmented coatings.
Hydroxyl-containing copolymers based on (meth)acrylates and reaction products of acrylic acid and glycidyl esters of .alpha.-alkylalkanemonocarboxylic acids and/or .alpha.,.alpha.-dialkylalkanemonocarboxylic acids which can be processed together with organic polyisocyanates to form coatings are known. DE-B-1 668 510 describes copolymers of addition products of .alpha.,.beta.-ethylenically unsaturated carboxylic acids with glycidyl esters and copolymerisable .alpha.,.beta.-unsaturated monomers with and without hydroxyl groups. DE-C-2 603 259 discloses two-component coatings containing specific binders. These binders are copolymers based on styrene, methyl methacrylate, acrylic acid and glycidyl esters of .alpha.-alkylalkanemonocarboxylic acids and/or .alpha.,.alpha.-dialkylalkanemonocarboxylic acids obtained by heating with simultaneous esterification and polymerization in inert solvents in the presence of polymerization initiators with or without chain terminators.
The solids contents of prior art copolymer solutions on termination of the simultaneous esterification and copolymerization is not more than 55% by weight or, according to page 4 of DE-A-3 740 774 (component A), about 65% by weight, although the objective of the latter reference was a particularly high solids content.